in Monthly Notices of the Royal Astronomical Society (2013), 429(3), 2500

γ Doradus stars pulsate with high-order gravity modes having typical frequencies which can be comparable to or higher than their rotation frequencies. Therefore, rotation has a non-negligible effect on ... [more ▼]

γ Doradus stars pulsate with high-order gravity modes having typical frequencies which can be comparable to or higher than their rotation frequencies. Therefore, rotation has a non-negligible effect on their oscillation properties. To explore the rotation-pulsation coupling in γ Dor stars, we perform a non-adiabatic study including the traditional approximation of rotation on a grid of spherical stellar models covering the mass range 1.4 < M[SUB]*[/SUB] < 2.1 M[SUB]&sun;[/SUB]. This approximation allows us to treat the effect of the Coriolis force on the frequencies and the stability of high-order g modes. The effect of the Coriolis force depends on the kind of mode considered (prograde sectoral or not) and increases with their periods. As a consequence, we first find that the period spacing between modes is no longer periodically oscillating around a constant value. Secondly, we show that the frequency gap (5-15 cycles day[SUP]-1[/SUP]) arising from stable modes between γ Dor-type high-order g modes and δ Scuti-type modes can be easily filled by g-mode frequencies shifted to higher values by the rotation. Thirdly, we analyse the combined effect of diffusive mixing and the Coriolis force on the period spacings. And finally, we predict a slight broadening of the γ Dor instability strip. [less ▲]

Context. The late A and F-type γ Doradus (γ Dor) stars pulsate with high-order gravity modes (g-modes). The existence of different evolutionary phases crossing the γ Dor instability strip raises the question whether pre-main sequence (PMS) γ Dor stars exist. <BR /> Aims: We intend to study the differences between the asteroseismic behaviour of PMS and main sequence (MS) γ Dor pulsators as predicted by the current theory of stellar evolution and stability. <BR /> Methods: We explore the adiabatic and non-adiabatic properties of high-order g-modes in a grid of PMS and MS models covering the mass range 1.2 M[SUB]&sun;[/SUB] < M[SUB]∗[/SUB] < 2.5 M[SUB]&sun;[/SUB]. <BR /> Results: We have derived the theoretical instability strip (IS) for the PMS γ Dor pulsators. This IS covers the same effective temperature range as the MS γ Dor one. Nevertheless, the frequency domain of unstable modes in PMS models with a fully radiative core is greater than in MS models, even if they present the same number of unstable modes. Moreover, the differences between MS and PMS internal structures are reflected in the average values of the period spacing, as well as in the dependence of the period spacing on the radial order of the modes, opening the window to determination of the evolutionary phase of γ Dor stars from their pulsation spectra. [less ▲]

The question of the existence of the pre-main sequence (PMS) γ Doradus (γ Dor) pulsators has been raised by observations of young clusters such as NGC 884 hosting γ Dor members. We have explored the ... [more ▼]

The question of the existence of the pre-main sequence (PMS) γ Doradus (γ Dor) pulsators has been raised by observations of young clusters such as NGC 884 hosting γ Dor members. We have explored the properties of γ Dor-type pulsations with a grid of PMS models covering the mass range {1.2 < M_*/M_ȯ < 2.5} and we derive the theoretical instability strip (IS) for the PMS γ Dor pulsators. We explore the possibility of distinguishing between PMS and MS γ Dor by the behaviour of the period spacing of their high order gravity modes (g-modes). [less ▲]

γ Doradus (γ Dor) are F-type stars pulsating with high order g-modes. Their instability strip (IS) overlaps the red edge of the δ Scuti δ Sct) one. This observation has led to search for objects in this ... [more ▼]

γ Doradus (γ Dor) are F-type stars pulsating with high order g-modes. Their instability strip (IS) overlaps the red edge of the δ Scuti δ Sct) one. This observation has led to search for objects in this region of the HR diagram showing p and g-modes simultaneously. The existence of such hybrid pulsators has recently been confirmed [10] and the number of candidates is increasing (e.g. [17]). From a theoretical point of view, non-adiabatic computations including a time-dependent treatment of convection (TDC) predict the existence of γ Dor/δ Sct hybrid pulsators ([5], [8]). Our aim is to confront the properties of the observed hybrid candidates with the theoretical predictions from non-adiabatic computations of non-radial pulsations including the convection-pulsation interaction. [less ▲]